(a) Field of the Invention
The invention relates to an image-scaling-down method and an image processing apparatus, particularly to an image-scaling-down method and an image processing apparatus which reduce the number of pixel data of a pixel block.
(b) Description of the Related Art
Generally, in a display device like a digital picture frame or television equipped with an image decoder for displaying the image corresponding to compressed image data with a format like JPEG, GIF, etc., at least one memory is needed to temporarily store the decoded image data and then the display device accesses the decoded image data stored in the memory for displaying this image. FIG. 1 schematically shows a portion of an image 11 including four pixel blocks 12. As shown in FIG. 1, the image compression technique utilizing the JPEG format treats each 8×8 pixel block 12 as one unit to perform compression and also treats each 8×8 pixel block 12 as one unit during decoding.
In the prior art, after the display device decodes the compressed image data, the decoded image data will be stored in a memory. As the image corresponding to the decoded image data has 10,000,000 pixels, the memory has to have the capacity of 10 M×3 bytes, that is, 30 MB. In addition, as the display device can only display a 1920×1080 image with 2,000,000 pixels, the display device according to the prior art has to convert the decoded image data into an output image data corresponding to the image with 2,000,000 pixels. Therefore, according to the prior art, the capacity of the required memory is relatively large and the capacity of the memory is wasted.